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<br />3~ <br /> <br /> <br />001853 <br /> <br />interception. surface deteTi'tion, and ipfiltration, to -give estimated <br /> <br />surfa.ce runoff. In the alternate method, multivariate analysis is, <br /> <br />used to relate the runoff to the preIJipitation, soil moisture, and <br /> <br />vegetation condition, and these relations are used to estimate su<r~ <br /> <br />face runoH; The results of either method may be- helpful in <br /> <br />adjusting known water yields from nearby areas. <br /> <br />Precipitation intensitie's- <br /> <br />. <br /> <br />Precipitation intensities and their frequencies maybe esti~ <br /> <br />mated from published preciI1itation records and summa'ries. Maps <br /> <br />of rainfall frequencies for durations from 30 minute's to 2..4 hours <br /> <br />and for return intervals frc;>m 1 to ~OO years have recently been <br /> <br />I " <br />published: by the Weather Bureau (Hershfield, 1961). The infor- <br /> <br />mation extracted from guidelil to precipit~tion intensities have been <br /> <br />, . <br />summarize4,:~or'\1arious subregions of the Pacific',S,outhwest (see <br /> <br />. <br /> <br />t;.b,le 2.). These intensities may be supplemented by referral to <br /> <br />l~~al precipitation station records anq. knowledge of orographic <br /> <br />and rain shadow effects. . S,ome extrapolation is generally neces- <br /> <br />sary for periods of le~s than 30 p:>inutes duration where small rUn- <br /> <br />off areas are involved and adJus~ments are neededdor conversio~ <br /> <br />of point-rainfall information to areal.amounts and'intensities and <br /> <br />where storms are known to be e'!:tremely limited in area' and highly <br />variable within th~ watershe411 The adjustmellts for short-time <br />intervals are shown on table 2.. <br />